#include<stdio.h>
double Factorial(double m);
int main()
{
	double number;
	double s;
	scanf("%lf",&number);
	s=Factorial(number);
	printf("%lf",s);
	return 0;
}
double Factorial(double m)
{
	double sub=1.0,i;
	for(i=1.0; i<=m; i++)
	{
		sub=sub*1/i;
	}
	return sub;
}

